ii STABILITY IN THE PAST 105 



the processes through which develop- 

 ment has been conducted. But exactly 

 the same may be said of the idea of 

 species being so unstable that they were 

 constantly passing into each other by 

 nothing but fortuitous and infinitesimal 

 variations. 



This, indeed, may be an easier and 

 lazier conception than any other. But 

 it is easier only because it takes no notice 

 of insuperable difficulties and disagree- 

 ments with the facts. Species have 

 been quite as stable throughout all the 

 geological ages as they are at present. 

 Linnseus's Binomial system of classifica- 

 tion is as applicable to, and fits as well 

 into, the Trilobites of the Palaeozoic rocks 

 the Brachyopods and the Cephalopods 

 of the Secondary ages the Mammalia 

 of the Tertiary epoch, as it fits into all 

 the species now alive or only recently 

 extinct. Each species has its own dis- 



